How to Identify and Classify Crabs
  • 1. Which feature is MOST important for initial crab classification?
A) Eye color
B) Claw size
C) Body shape
D) Leg length
  • 2. What is the difference between true crabs and false crabs?
A) True crabs have a reduced abdomen tucked under the cephalothorax
B) False crabs live only in freshwater
C) False crabs are larger
D) True crabs have more legs
  • 3. Which crab shape is characteristic of Brachyura (true crabs)?
A) Broad and flattened
B) Star-shaped
C) Round and bulbous
D) Long and narrow
  • 4. What term describes the fused head and thorax of a crab?
A) Carapace
B) Cephalothorax
C) Abdomen
D) Prosoma
  • 5. Which appendage is typically modified into large claws in crabs?
A) Uropods
B) Pereiopods
C) Chelipeds
D) Pleopods
  • 6. How many pairs of walking legs do most true crabs have?
A) Five
B) Three
C) Six
D) Four
  • 7. The small abdominal flap on the underside of a crab is used for what?
A) Camouflage
B) Reproduction
C) Digging
D) Swimming
  • 8. How can you typically determine the sex of a crab?
A) By the length of the legs
B) By the shape of the abdominal flap
C) By the size of the claws
D) By the color of the carapace
  • 9. A wide, U-shaped abdominal flap generally indicates a:
A) Juvenile crab
B) Male crab
C) Hermaphrodite crab
D) Female crab
  • 10. A narrow, V-shaped abdominal flap generally indicates a:
A) Hybrid crab
B) Female crab
C) Male crab
D) Immature crab
  • 11. What is the function of gills in crabs?
A) Waste removal
B) Oxygen extraction
C) Food digestion
D) Sensory perception
  • 12. Where are crab gills typically located?
A) Externally, attached to the body
B) On the abdomen
C) On the legs
D) Within the gill chambers beneath the carapace
  • 13. What is the function of the crab's carapace?
A) Digestion
B) Locomotion
C) Respiration
D) Protection
  • 14. Which of these is a key feature to identify spider crabs?
A) Large, symmetrical claws
B) Paddle-like swimming legs
C) Long legs relative to their body size
D) Brightly colored carapace
  • 15. Which crabs are known for their ability to run sideways quickly?
A) Hermit crabs
B) King crabs
C) Stone crabs
D) Ghost crabs
  • 16. What type of crab is known for carrying a shell for protection?
A) Box crab
B) Snow crab
C) Fiddler crab
D) Hermit crab
  • 17. What distinguishes fiddler crabs?
A) A flattened, shovel-like carapace
B) One greatly enlarged claw in males
C) The ability to climb trees
D) Brightly colored walking legs
  • 18. Which crab is commonly found in saltwater marshes and mudflats?
A) Pea crab
B) Coconut crab
C) Decorator crab
D) Mud crab
  • 19. What is the scientific term for molting in crabs?
A) Osmoregulation
B) Metamorphosis
C) Ecdysis
D) Regeneration
  • 20. Why do crabs molt?
A) To grow larger
B) To change color
C) To shed parasites
D) To reproduce
  • 21. What is the 'crab' in 'horseshoe crab'?
A) They were once classified as crabs but have since been reclassified.
B) An accurate descriptor, it's a type of crab.
C) A misnomer, they are more closely related to spiders and scorpions.
D) A regional term for a certain type of true crab
  • 22. Which of these is NOT a feature typically used for crab identification?
A) Leg structure
B) Internal organ structure
C) Claw shape
D) Carapace ornamentation
  • 23. The teeth-like projections along the front edge of a crab's carapace are called:
A) Epipods
B) Marginal setae
C) Branchial ridges
D) Rostral spines
  • 24. What is the primary diet of most crabs?
A) Herbivorous
B) Carnivorous
C) Omnivorous
D) Detritivorous
  • 25. Which adaptation allows some crabs to survive out of water for extended periods?
A) Ability to absorb oxygen through their skin
B) Specialized lungs
C) Waterproof carapace
D) Modified gill chambers
  • 26. What is the function of the uropods in some crab species?
A) Feeding
B) Sensing vibrations
C) Defense
D) Swimming
  • 27. Which group are considered 'false crabs' because of their flattened shape, despite not being true crabs?
A) Shore crabs
B) Hermit crabs
C) Spider crabs
D) King crabs
  • 28. What is the name of the larval stage of a crab?
A) Zoea
B) Nauplius
C) Megalopa
D) Cyprid
  • 29. Which crab is known for its bright red color and is often harvested for food?
A) Snow crab
B) Dungeness crab
C) Red king crab
D) Blue crab
  • 30. How do crabs communicate?
A) They don't communicate
B) Through visual and chemical signals
C) Primarily through vocalizations
D) Only through tactile signals
Created with That Quiz — where test making and test taking are made easy for math and other subject areas.